Accessing Subtype Items From Generic Collections?
Oct 29, 2009
I've hit a problem with the way I am using generics and I suspect that my design isn't quite right. I have a base class
AbstractBaseClass
inherited by
InheritingOneClass
[code]....
I have a generic list IList(of T as AbstractBaseClass) which I am populating with instances of the various inheriting classes. Now I can cycle through the list BUT depending on which subtype the item is, I want to pass the item to various functions (or instantiate various classes) which access properties/methods of the inheriting Class. I don't really want to have to use a Select Case and list all the potential types of the Inheriting classes. Is there a mechanism I can put in place to automate this?
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Dec 16, 2009
We have migrated our Vb6 application to VB.NET using a third party tool. Now we are in a process of Refactoring and introducing object oriented concepts in the application.
In VB6, we were using structures in many places. As a part of introducing object oriented programming,
1. is it a good idea of changing all Structures to Classes? or Is there a concept of "Generic Structure" similar to Generic collections, Generic classes?
2. Can some one guide me any source containing guide lines or best practices for applications that are migrated to VB.NET from VB6 and implementing object oriented programmaing.
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Sep 21, 2011
I'm having a problem with this code in the highlighted line(*); getting the error in the heading.
Dim htmlarraylist As New List(Of iTextSharp.text.IElement)
htmlarraylist = *HTMLWorker.ParseToList(New StreamReader(tempFile), New StyleSheet())*
[Code].....
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Feb 5, 2011
[code]...
What's really the point in using the former?It's hard to use linq if I used the former. I have to convert that to an array first which is difficult because there is no (asarray) function.I think I would change all of my code that's using System.
Collections.Specialized.StringCollection to System.Collections.Generic.List(Of String)
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Aug 24, 2009
I have a parent class and many children class, right now it look like this:
Public Class Parent
Public Property ID as String
End Class
[Code].....
What I need is a strongly type list List(Of Child) that Inherits from ListOfParent (I need the FindByID method) but I can't find the right syntax.
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Nov 29, 2010
Is there an exhaustive list of all of the "base" (not used in an object-oriented sense but more in a common sense) generic types in the 4.0 .NET Framework? I have found this list that I often send newer/mid-level devs to so they can understand how non-generic types map to generic types, but this is by no means exhaustive. I'm looking for something that also includes things such as KeyValuePair<>, Tuple<>, and other basic generics that may not be very-well known. Interfaces such as IObservable<> would be nice but not necessarily required.
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Jun 19, 2012
If i have an object that implements an interface (and don't know the exact object) i can call a sub (DoSomething) by going:
vb
Dim iObj = trycast(something, iInterface)
if iObj isnot nothing then
iObj.DoSomething()
end if
How can I do this for a Generic? such as...
vb
Public Class TestClass(of T)
Public sub DoSomething()
....
end class
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Mar 25, 2011
I am new to VB.NET, just landed a job fresh out of school (well still in school), but I am having trouble with VB...alot of it is getting used to the IDE itsself (we use VB 2010).t does alot of the work for you which is cool but I am having some trouble understanding some concepts.Here are my questions: How to call classes named an initialized on a DSS skeleton to a new page. And the functionalities of building a collection. (also the differences of a generic
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Jan 27, 2010
imagine i want to add an extension method to System.Collections.Generic.List(Of T)
let's say i want to give it .GetUBound which returns Count-1
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Jan 3, 2012
given the following class structures:[code]I add the following property to MyList, trying to answer questions like "find out the number of elements with specified type, say Derived1, inside MyList?"[code]
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Feb 2, 2012
I have a lists of different custom classes and each must be sorted severals times before the algorithm is complete. For each sort I wrote a comparer. Sofar so good. Everything works. But: By now I have abou a dozen different comparers in more than one class and it is still getting more. I wonder if there is a way to limit the number by writing a new general function that can be used to sort all lists without the need for a specific comparer.Below is what I've got so far. But it does not work.
"System.Collections.Generic.List(Of ClassA)" can not be converted into "System.Collections.Generic.List(Of Object)."
[code].....
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May 20, 2011
If i wish to put items into a System.Collections.Generic.Dictionary, I can either Add or set the Item.I know if you do Add it helps you check if the key already exists and if not it throws an exception.Now I'm curious, so if I'm adding a ton of items, should I prefer setting Item instead of Add since Add does unnecessary checks that may actually slow things down?
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Jun 10, 2012
I am trying to pass a System.Collections.Generic.List to another class. The collection is created in class2 and then passed into class1
[code]...
However I get a 'Null Reference Exception error' when I run the program. It seems f_str in the line 'For Each s As String In f_str' is null.
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Sep 21, 2011
I am planning to use a List in my application but when I was searching for System.Collections.Generic, it only has System.Collections. I tried to look it up in the "add reference" and its not there.
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Feb 15, 2009
how to find a value in the System.Collections.Generic.List.I have:
Private ids As New List(Of Byte())
ids.add(New Byte(){&HA8,&H0F})
ids.add(New Byte(){&HFF,&H03})
ids.add(New Byte(){&H10,&H00})
I would like to find for example: &H10,&H00 in that list and if there isn't the stuff I wan't to find then how do I know that?
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Apr 10, 2012
I need to be able to tell if a property is of type List(of T)but am currently unable to. if i do
TypeOf (UpdateTo.GetType.GetProperty(node.Name)) Is System.Collections.Generic.List(Of Object)
I get the following error
TypeOf (UpdateTo.GetType.GetProperty(node.Name)) Is
System.Collections.Generic.List(Of Object) Expression of type
'System.Reflection.PropertyInfo' can never be of type[code]......
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Mar 12, 2009
I want to write a generic file saving routine where the routine is passed data in the form of a collection and it sets a containsStructure flag. I wanted to be able to save the data from the collection, but if it is a collection of structures I want to be able to extract the data from the structure to write to the file.
The only trouble is, that I cannot do something like:
For Each s As dataStructure In data
Next
Since the compiler complains that dataStructure is not defined. Is there a way to code around this?
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May 20, 2011
in what situation will an item in System.Collections.Generic.List not be removed successfully?url...The way they phrase it makes me think that it is possible that a Remove operation on an item found in the List(Of T) could actually fail.
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Mar 20, 2009
I need another (dozen) pair of eyes on this. The following code:
Interface iRuleEntity
Function GetRuleViolations() As List(Of RuleViolation)
End Interface
Partial Public Class Feedback
[code]....
is giving me this error:'Feedback' must implement 'Function GetRuleViolations() As System.Collections.Generic.List(Of RuleViolation)' for interface 'iRuleEntity'.
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Feb 12, 2011
This code:
vb Dim s As String = strContents '<a global variable) Dim currentPos As Int64 = 0 Dim endPos As Int64 = strContents.Length - 1 '// A dictionary, used to count the frequencies Dim characterCounter As New Dictionary(Of [String], Int64)() While currentPos <> endPos '//
[CODE]...
Gives this error: Value of type 'System.Collections.Generic.KeyValuePair(Of String, Long)' cannot be converted to 'System.Collections.DictionaryEntry'.
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Jan 26, 2010
have a collection that stores structures of data. my problem is that, after i have populated my collection, i do not know how i could change or update the data stored in the collection.my structure of data looks like this:
Structure tType1
Dim ID as Integer
Dim QTY as Integer
[code].....
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May 3, 2012
i have issue returning a list in a web method. here is the code
<WebMethod()> _
Public Function getTags(para_parents As String) As List(Of getTypeDetailsByParentName_Result)()
Dim context As New PPEntities
[code]....
the error is
Value of type 'System.Collections.Generic.List(Of SaftyonRoad.getTypeDetailsByParentName_Result)' cannot be converted to '1-dimensional array of System.Collections.Generic.List(Of SaftyonRoad.getTypeDetailsByParentName_Result)'
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Apr 1, 2011
I have a number of idential repeaters, and I need to iterate through all of the items. I currently have:
For Each item In rpt1.Items
.do some stuff
Next[code]....
Is there a simple way to reduce this to a single For Each ... Next loop?
Edit: There are a number of local vars involved in "do some stuff", which is why I can't just pass the item into a function - the call would have to include about 8 ByRef params.
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May 14, 2012
I'm getting an error after sending a list to a web service.This is the code that is calling the web service:
Dim sProgramInterest As New List(Of Integer)
crmService.InsertProspectGetId(sProgramInterest.ToList)
But I'm getting this error.
[code].....
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Jul 7, 2010
I have created a Dictionary class (MyDictionary for the example). I am currently trying to pass MyDictionary into a function, filter it into a new instance of MyDictionary and pass this new instance into another method. When I am attempting to create the second instance from the filtered first instance of MyDictionary via Lambda Expressions and the ToDictionary Method, I am getting the following error:
Unable to cast object of type 'System.Collections.Generic.Dictionary`2[System.Int32,System.String]' to type 'MyDictionary'. I have simplified the example and recreated it in LINQPad and am getting the same error.
Here's the simplified version of my code:
[Code]...
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Jan 7, 2012
And here is the code that produces the error
CODE:
How can i cast this one?
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Mar 12, 2009
I have converted c# .cs to vb:= I have 6 errors on:
Red "List" says Too few type arguments to system.Collections.Generic.List(Of T)'
Orange "Calendar" says Value of type 'System.Windows.Forms.Control.ControlCollection' cannot be converted to 'Form1.Kobush.Windows.Forms.Appointment'.
[code]....
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Jan 17, 2011
I have a problem with adding items to generic list, problem is when I add 1. item to the list, everything is ok, but when I add second, first and second has the same values...
This is code (asp.net 4.0):
Partial Class _Default
Inherits System.Web.UI.Page
<Serializable()>
Public Class Product
Shared Property Material As String
[URL]
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Feb 11, 2010
I've added a DataGridViewComboBoxColumn to a datagridview and it displays items ok but what I want to do now is have a default item selected, rather than show up empty or as a "Please select" message.
[Code]...
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Nov 6, 2011
I have created a list of another class and loaded the list with data. using breakpoints I can see that the data is loading and visible in my form page. However, when I attempt to access the list using a For Each loop, I get an error saying that "Value of type Customer can not be converted to Integer"I am trying to follow examples from tutorials on accessing list elements, but they are never lists of objects, so I am not sure what I am doing wrong.
My class that I have made a list of:
Public Class Customer
Private m_firstName As String
[code]......
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